A majority of hitters who have faced the Reds' 2011 first-round Draft pick since then have struggled to find the same luck.
Stephenson allowed just one more hit in the next four innings of work and struck out eight to cap off a much-anticipated Minor League debut with the Rookie-level Billings Mustangs on June 19, and the success has carried with him throughout the 2012 season.
"The hitters are just so much better than high school hitters," said Stephenson, who has 11 starts under his belt this year. "Consistently better."
It sure doesn't seem that way for the Martinez, Calif., native.
Stephenson, a former Alhambra High School standout, was promoted to Class A Dayton a month later after seven starts, in which he went 1-0 with a 2.05 ERA in 30 2/3 innings.
The 27th overall pick in the 2011 First-Year Player Draft struck out the first three batters he faced in his debut with Dayton on June 27, and even fired a fastball that broke the triple-digit mark on the radar gun.
Stephenson allowed just one hit and an unearned run through five innings of work to earn a win in his first start with the Dragons, and he has posted a 2-0 record and a 3.00 ERA in four starts this season.
"It's mostly been a lot of fun and really exciting," said Stephenson, who didn't sign with the Reds until mid-August last year, delaying the start to his professional career. "When I first started out, it was a little boring because it was moving a little slowly. The last few weeks have been really exciting."
The 6-foot-2 righty is the first high school pitcher the Reds have drafted in the first round since they took Homer Bailey with the seventh overall pick in 2004.
Stephenson has yet to record a loss in the Minors, holding a combined 3-0 record with a 2.30 ERA in 11 starts, and Reds assistant director of player development Jeff Graupe said the club has been extremely impressed with Stephenson's velocity, which ranges from 93-99 mph, and has touched as high as 101.
"He's an intelligent young man, and physically, his arm strength is top of the charts," Graupe said. "For a starting pitcher to be able to carry that [velocity] for six or seven innings, that's pretty impressive."
The hard-throwing right-hander has chalked up 57 strikeouts with just 15 walks this season while recently working on adding a changeup to his arsenal -- a pitch he didn't throw in high school, when he resorted to a split-finger fastball instead.
"I mostly rely on the fastball to get ahead," Stephenson said. "I try to back them on fastballs, and if I get ahead in the count, I go to offspeed. [The changeup] is something I just started throwing in the past year. I got a really good feel for it when I was in Billings, then I kind of lost feel for it, so I haven't been throwing it quite as much recently."
Stephenson has given up 32 hits and just three homers this season, and he boasts a 0.97 WHIP through 48 2/3 innings in 2012. The organization is currently overseeing Stephenson's workload, typically limiting him to 70 pitches or five innings per start.
Graupe said the toughest transition for a high schooler making his way through the professional ranks is the rigorous workload of a full-time baseball player. He said Stephenson is "thriving" in the daily schedule of a pitching rotation, and said the 19-year-old gunslinger is right on pace in his development.
"Amazingly, for a guy like Robert -- who has the velocity he has -- there isn't a ton of effort in his delivery," Graupe said. "So while we are monitoring his innings and his pitches at this point, he'll be able to grow at a healthy rate over the next couple years to a point where I think he's physically strong and durable enough to where he'll take a pretty big workload."
Stephenson said he didn't know the details of the plan the staff has for him, but he did have one personal goal for his future.
"Within five years, I definitely want to be in the big leagues," Stephenson said.
Mark Clements is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.